Lab Values

CBC: Complete Blood Count

• The complete blood count (CBC) is one of the most commonly ordered blood tests.
• The complete blood count is the calculation of the cellular (formed elements) of blood.
• A major portion of the complete blood count is the measure of the concentration of white blood cells, red blood cells, and platelets in the blood.

White Blood Cell Lab Values

■ Description: WBC primary function is to fight infection

• Precautions and Considerations
  – Elevated levels usually indicate infections

  • Patient may present with fever, malaise, lethargy

  • Decreased levels may indicate infection and immunocompromised state

    • Patient at high risk for additional infection

    • May need to implement Neutropenic Precaution

Red Blood Cell Lab Values

■ RBC values consist of three parts:
– Hemoglobin: protein contained in RBCs that delivers oxygen to tissues
– Hematocrit: measures volume of RBCs compared to total blood volume
– Platelets: blood cells that form clots
■ Hemoglobin and Hematocrit values vary between male and female
■ Platelets are the same for male and female

Prothrombin time (PT)

measures speed of clotting by means of the extrinsic pathway

• for coumadin

International normalized ratio (INR)

used to correct for differences in lab reagents to test PT

Partial thromboplastin time (PTT)

measures speed of clotting by means of two consecutive series of biochemical reactions (intrinsic pathway and common pathway of coagulation)

Activated partial thromboplastin time (aPTT)

activator added that speeds up clotting time and results in more narrow reference range

• for heparin

coagulation

Often patients are given heparin as a bridge to long term anti-coagulation therapy (ie, Warfarin) during that time aPTT is the lab value to monitor. Once a patient transitions to Warfarin, INR is then used to assess clotting risk

electrolytes

■ Electrolyte balance required for nerve conduction, muscle contraction/relaxation, cardiac rhythm/conduction, bone health, blood coagulation, and maintenance of proper fluid balance in the body.
■ Balance mostly controlled by kidneys plus neurologic, endocrine, GI, and MS
■ Electrolyte disorders frequent and challenging problem in acute care

Creatinine Kinase (CK)

– CK1-BB (brain tissue), CK2-MB (cardiac muscle), CK3-MM (skeletal muscle)
■ Description: measurement of creatinine kinase (CK) levels in the blood
– Elevated after MI, skeletal muscle injury, strenuous exercise
■ Precautions and considerations:
– Elevated 4-6 hours after MI, peaks 12-24 hours after MI, clears about 48-72 hours
– Activity should be limited or held when CK trend is rising
– Activity can continue once CK trends down toward normal range

troponin

• Description: protein involved in muscle contraction; used as a diagnostic marker for heart disorders and MI (elevates after MI)
  ■ Precautions and considerations:
  – Troponin enzyme begins rising at 8 hours after MI, peaks at 12-16 hours, returns to normal within 1 week
  – Normal Troponin < .03 ng/mL
   Higher levels may indicate myocardial damage, demand ischemia, or renal and/or vascular problems
  ■ May need to hold activity until 24 hours after troponin peak and it begins trending down

BNP levels < 100 pg/mL

no heart failure

BNP levels 100-300 pg/mL

HF present

BNP levels 300-600 pg/mL

mild HF

BNP levels 600-900 pg/mL

moderate HF

BNP levels > 900 pg/mL

severe HF

NT-proBNP

■ Longer half-life than BNP and not affected by ARNI drugs
■ Norms vary with age
– >50 yrs old: 300-450 pg/mL
– 50-74 yrs old: 300-900 pg/mL
– 75 and older: 450-1800 pg/mL
■ May provide more accurate detection of heart failure than BNP

acid base disorders

■ Acid-base balance: equilibrium of pH in extracellular fluid
■ Range of pH necessary for life: 6.8 to 7.8
■ Respiratory and renal systems responsible for maintaining acid-base balance
– Hyperventilation lowers arterial CO2 increased pH
– Kidney disease decreases renal bicarbonate decreased pH
■ Acid-base imbalance
– Acidosis or alkalosis
– Metabolic or respiratory or mixed

respiratory alkalosis

– Elevated pH associated with reduced PaCO2
– Arterial CO2 < 35 mmHg; pH ≥ 7.45
– Hyperventilation
– Associated with nervousness, anxiety, pain, pregnancy, PE

respiratory acidosis

– Reduced pH associated with elevated PaCO2
– Arterial CO2 > 45 mmHg; pH ≤ 7.35
– Hypoventilation
– Associated with COPD, pneumonia, sleep apnea, head trauma

metabolic alkalosis

– Elevated pH associated with loss of normal metabolic acids
– Arterial HCO3- > 27 mEq/L; pH ≥ 7.45
– Associated with severe vomiting, excess use of antacids, diuretics, hypokalemia

metabolic acidosis

– Reduced pH associated with deficit of bicarbonate (HCO3-)
– Arterial HCO3- < 23 mEq/L; pH ≤ 7.35
– Associated with chronic diarrhea, shock/sepsis, trauma, diabetic ketoacidosis, renal failure/uremia, hypoxia

Blood Urea Nitrogen (BUN)

6.0-21.0 mg/dL
■ Urea forms in the liver from breakdown of proteins, amino acids; kidneys
responsible for excreting urea
■ Description: BUN measures renal excretory capacity and estimates protein
catabolism and/or tissue necrosis
■ Elevated levels indicate renal disease (i.e., acute or chronic renal failure), high
protein diet, decreasing volume (hypovolemia), CHF
■ Decreased levels uncommon; can result from malnutrition (low protein
intake)

Creatinine

0.8-1.4 mg/dL
■ End product of muscle metabolism, detects GFR
■ Increased levels: any renal or metabolic impairment

estimated GFR

≥ 60 mL/min
■ Measures level of kidney function and determines stage of kidney disease
■ Stage 1 (normal): ≥ 90 mL/min
■ Stage 2 (mild): 60-89 mL/min
■ Stage 3a (mild-mod): 45-59 mL/min
■ Stage 3b (mod-severe): 30-44 mL/min
■ Stage 4 (severe): 15-29 mL/min
■ Stage 5 (kidney failure): < 15 mL/min (requires dialysis)

Alkaline phosphotase (ALP)

enzyme produced in liver and bone
– increases with abnormal bone growth, liver damage

Aspartate aminotransferase (AST)

enzyme present in tissues of high metabolic activity (liver, skeletal and cardiac muscle)
– increases with impaired hepatocytes, myocardial cells, RBCs, muscle cells

Alanine aminotransferase (ALT)

catalyzes chemical reaction that creates pyruvate from alanine for gluconeogenesis
– increases with impaired hepatocytes, myocardial cells, RBCs, muscle cells

Bilirubin

breakdown product of hemoglobin, transported to liver, excreted in bile
– increases with liver damage, jaundice

glucose

0-100 mg/dL [fasting plasma glucose (FPG): 90-130 mg/dL]
– Measure of immediate blood glucose level (usually after 12-14 hour fast)
– < 70 mg/dL: patient needs carbs before activity
– > 240 mg/dL: hold activity until patient receives insulin

Hemoglobin (Hgb) A1C

normal value: <5.7% (usually between 4-6%)
– Indicator of blood glucose level for past 3 months
– Pre-diabetic: 5.7-6.4%
– DM: > 6.5%

ammonia

converted to urea and normally excreted quickly in urine; very toxic to body and affects acid-base balance.
– Normal range: 10-40 micromol/L
– Elevated levels due to renal disease, hepatic dysfunction

serum albumin

used to assess nutritional status, half-life of 21 days
– Normal range: 3.5-5.0 g/dL
– < 3.0 nutritional compromise; <2.8 poor wound healing

Serum pre-albumin

more accurate indicator of recent nutritional status due to shorter 2-day half-life
– Normal range: 16-30 g/dL
– < 10 poor nutritional status, impaired wound healing